Tactile sensor module for robot-hand and grasping method using the same

Abstract

This disclosure relates to a technology for grasping an object while adjusting a grasping force according to stiffness of the object measured by a tactile sensor module, especially to a robot-hand, which includes a tactile sensor module for measuring a normal force applied when grasping an object, a phalange sensor module having an actuator to generate a driving force and configured to measure a rotational displacement of a motor, and a hand back control unit for operating the actuator by generating a desired displacement signal to control a grasping force so that a grasping motion is stably and accurately achieved by applying a minimum grasping force to soft object with no sliding and minimized deformation, wherein the desired displacement signal is generated based on stiffness which is calculated from the normal force data and the rotational displacement data.

What is claimed is: 
     
       1. A tactile sensor module for a robot-hand, comprising:
 a force sensor configured to measure a normal force applied when the robot-hand is grasping an object; 
 a Flexible Printed Circuit Board (FPCB) assembly having an inclined surface to which the force sensor is mounted to form a plurality of rows, the FPCB assembly being configured to supply a power to the force sensor; 
 a stress transfer element formed at an upper portion of the FPCB assembly to be spaced apart therefrom to accommodate the force sensor therein, the stress transfer element being configured to transfer the normal force applied by the object to the force sensor; and 
 a fingertip control unit configured to collect, correct and output normal force data measured by the force sensor. 
 
     
     
       2. The tactile sensor module according to  claim 1 ,
 wherein the stress transfer element is made of a urethane rubber and formed on the FPCB assembly by casting and curing. 
 
     
     
       3. A robot-hand, comprising:
 a plurality of fingers, each having a tactile sensor module and a plurality of phalange sensor modules rotatably coupled by link members; and 
 a base connected with the plurality of fingers by a base link member and having a hand back control unit for controlling a grasping motion of the finger, the base having a cover plate installed at an outer surface thereof, 
 wherein the tactile sensor module is configured to measure a normal force applied when the robot-hand is grasping an object, 
 the phalange sensor module has an actuator to generate a driving force for a grasping motion and is configured to measure the normal force and a rotational displacement of a motor of the actuator when the robot-hand is grasping the object, and 
 the hand back control unit is configured to control a grasping force by receiving the normal force data and rotational displacement data from the tactile sensor module and the phalange sensor module. 
 
     
     
       4. The robot-hand according to  claim 3 ,
 wherein stiffness of the object is measured from said normal force data and said rotational displacement data, and 
 the hand back control unit generates a desired displacement signal based on the stiffness and transfers the desired displacement signal to the actuator in order to control the grasping force applied to the object. 
 
     
     
       5. The robot-hand according to  claim 3 ,
 wherein the tactile sensor module includes: 
 a force sensor configured to measures the normal force applied when the robot-hand is grasping the object; 
 a FPCB assembly having an inclined surface to which the force sensor is mounted to form a plurality of rows, the FPCB assembly being configured to supply a power to the force sensor; 
 a stress transfer element formed at an upper portion of the FPCB assembly to be spaced apart therefrom to accommodate the force sensor therein, the stress transfer element being configured to transfer the normal force applied by the object to the force sensor; and 
 a fingertip control unit configured to collect, correct and output normal force data measured by the force sensor. 
 
     
     
       6. The robot-hand according to  claim 5 ,
 wherein the stress transfer element is made of a urethane rubber and formed on the FPCB assembly by casting and curing. 
 
     
     
       7. The robot-hand according to  claim 3 ,
 wherein the phalange sensor module includes: 
 a force sensor configured to measure the normal force applied when the robot-hand is grasping the object; 
 a Printed Circuit Board (PCB) assembly having a first PCB having an outer surface on which a plurality of force sensors are attached and a second PCB coupled to face the first PCB by a connection FPCB, the PCB assembly being configured to supply a power to the force sensor; 
 a stress transfer plate formed at an upper portion of the first PCB to be spaced apart therefrom to accommodate the force sensor therein, the stress transfer plate being configured to transfer the normal force applied by the object to the force sensor; 
 a phalange control unit configured to collect, correct and output normal force data measured by the force sensor; and 
 an actuator installed between the first PCB and the second PCB to generate a driving force for a grasping motion. 
 
     
     
       8. The robot-hand according to  claim 7 ,
 wherein the motor of the actuator includes a position sensor for measuring a rotational displacement when the robot-hand is grasping the object, and 
 the phalange control unit is configured to collect and output the rotational displacement data, and to transfer said normal force data and said rotational displacement data to the hand back control unit. 
 
     
     
       9. The robot-hand according to  claim 7 ,
 wherein the stress transfer plate is made of a silicone molding material and formed on the PCB assembly by casting and curing. 
 
     
     
       10. A grasping method for grasping an object using a robot-hand having a tactile sensor module at a finger, the grasping method comprising:
 generating a velocity command in a grasping direction so that the tactile sensor module contacts the object, and grasping the object by the robot-hand; 
 determining whether any force sensor provided to the tactile sensor module is activated as a normal force over a threshold value is applied to the force sensor; 
 counting a number of activated force sensors; 
 determining whether the number of activated force sensors is greater than a predetermined value; 
 maintaining a grasping motion of the robot-hand during a predetermined time; 
 generating a velocity command in a reverse grasping direction to decrease a grasping force of the robot-hand; and 
 determining whether the number of activated force sensors is equal to the predetermined value. 
 
     
     
       11. The grasping method according to  claim 10 ,
 wherein the robot-hand further includes a base connected to a plurality of fingers by a base link member, the base having a hand back control unit for controlling a grasping motion of the finger and a cover plate installed at an outer surface thereof, 
 the finger including a tactile sensor module and a plurality of phalange sensor modules rotatably coupled by link members, 
 the tactile sensor module is configured to measure a normal force applied when the robot-hand is grasping the object, 
 a phalange sensor module has an actuator to generate a driving force for a grasping motion and is configured to measure the normal force and a rotational displacement of a motor of the actuator when the robot-hand is grasping the object, and 
 the hand back control unit is configured to control a grasping force by receiving normal force data and rotational displacement data from the tactile sensor module and the phalange sensor module. 
 
     
     
       12. The grasping method according to  claim 11 ,
 wherein stiffness of the object is measured from said normal force data and said rotational displacement data, and 
 the hand back control unit generates a desired displacement signal based on the stiffness and transfers the desired displacement signal to the actuator to control the grasping force applied to the object. 
 
     
     
       13. The grasping method according to  claim 10 ,
 wherein the tactile sensor module includes: 
 a force sensor configured to measure a normal force applied when the robot-hand is grasping the object; 
 a FPCB assembly having an inclined surface to which the force sensor is mounted to form a plurality of rows, the FPCB assembly being configured to supply a power to the force sensor; 
 a stress transfer element formed at an upper portion of the FPCB assembly to be spaced apart therefrom to accommodate the force sensor therein, the stress transfer element being configured to transfer the normal force applied by the object to the force sensor; and 
 a fingertip control unit configured to collect, correct and output normal force data measured by the force sensor. 
 
     
     
       14. The grasping method according to  claim 11 ,
 wherein the phalange sensor module includes: 
 a force sensor configured to measure a normal force applied when the robot-hand is grasping the object; 
 a PCB assembly having a first PCB having an outer surface on which a plurality of force sensors are attached and a second PCB coupled to face the first PCB by a connection FPCB, the PCB assembly being configured to supply a power to the force sensor; 
 a stress transfer plate formed at an upper portion of the first PCB to be spaced apart therefrom to accommodate the force sensor therein, the stress transfer plate being configured to transfer the normal force applied by the object to the force sensor; 
 a phalange control unit configured to collect, correct and output normal force data measured by the force sensor; and 
 an actuator installed between the first PCB and the second PCB to generate a driving force for a grasping motion. 
 
     
     
       15. The grasping method according to  claim 14 ,
 wherein the motor of the actuator includes a position sensor for measuring a rotational displacement when the robot-hand is grasping the object, and 
 the phalange control unit is configured to collect and output the rotational displacement data, and to transfer said normal force data and said rotational displacement data to the hand back control unit.